1. Field of the Invention
This invention pertains in general to the field of pneumatic apparatus for operation of a door and in particular to a pneumatic control mechanism for opening and closing a sliding door on a nautical vessel.
2. Description of the Prior Art
A large number of boats include at least one sliding door between the outside deck of the boat and the inside of a cabin. On larger boats or ships, many such sliding doors are used. In such applications, a sliding door is preferred over a hinged, swinging type of door because of space considerations and the negative aspects of a hinged door suddenly swinging in either direction due to rolling seas. A swinging door could severely injure a person when he or she is trying to enter or exit through such door when the rolling of the boat due to rough seas suddenly swings the door toward the person.
While sliding doors are preferred on a marine vessel, they are also subject to rapid opening or closing in an unrestrained condition due to rough seas. Thus, when a sliding door is unlatched, it will slide back and forth in its tracks depending upon the rolling or pitching motion of the boat and the location of the door. The result is that the door slams open or closed with a great deal of force. If a person is attempting to pass through the doorway associated with such a sliding door at the same time the boat is rocking, it is very probable that the person will be injured. Moreover, the constant rocking of the boat and therefore the slamming back and forth of a sliding door can cause damage to the boat and the door.
In order to negate the force effects of an unrestrained sliding door, the usual practice is to latch the door either in an open or a closed position. Latching of a sliding door is not, however, a complete solution to the problem. For example, when a latched-shut door is unlatched, preparatory to being open to allow a person or persons to pass therethrough, the rocking and/or rolling movement of the boat causes the door to move rapidly in either or both directions. To overcome this effect, the person must hold onto the edge of the door in an attempt to control the forceful motion of the door. Frequently, the person himself is trying to maintain his own balance and trying to control the movement of the door at the same time. Often, the result is a clumsy effort which is not successful and the door may slam against some part of the person causing him serious injury.
With the sliding door latched in an open position, passage therethrough in a safe and orderly manner is assured. But, the negative effects of the door always being open exist. The disadvantages of a latched-open door during foul or rainy weather conditions is obvious. Besides, why have a door if it is in the open position at all or most times?
In the prior art, most of the door control apparatus is designed for swinging doors. However, the door control apparatus intended for use with a swinging door is not adaptable to a sliding door, particularly where the swinging door apparatus includes articulated lever arms. In the category of door control apparatus which is adaptable to a sliding door, that is, those door controls which utilize a piston and cylinder which move in an axial direction, such prior art apparatus do not satisfactorily control the motion of a sliding door on a boat. There are a number of reasons for this deficiency. One is that the door apparatus will bias the door in either the open or closed direction while requiring force to move the door in the other direction. Therefore, with this type of door control apparatus, either a shut door or open door condition is imposed the opposite condition is achieved by overcoming the biased spring force and the hydraulic pressure force. To compensate for this condition, pneumatic pressure bleeding valves are incorporated in the pneumatic mechanism and/or a double-acting piston is used. While such apparatus does exist in the prior art, it does not offer a complete solution. One problem comprises a loss of power, either electrical or pneumatic. A loss of power could freeze the door in a closed position, which is totally unacceptable in an emergency. Another problem concerns the force used to close the door. A high force which may be necessary in rolling seas could injure a person momentarily stuck in the door opening.
Accordingly, a primary object of the present invention is to provide pneumatic control apparatus for a sliding door particularly adapted for marine use.
Another object of the present invention is to provide pneumatic control apparatus for use with a sliding door which allows for emergency manual opening or closing of the door.
Another object of the present invention is to provide pneumatic control apparatus for a sliding door which is fail-safe.
Another object of the present invention is to provide pneumatic control apparatus for a sliding door which prevents injury to a person from the force of closing the sliding door.
The above-stated objects as well as other objects which, although not specifically stated, but are intended to be included within the scope of the present invention, are accomplished by the present invention and will become apparent from the hereinafter set forth Detailed Description of the Invention, Drawings, and the claims appended herewith.